Schnabel is German for beak, like a birds beak.
Up side:
1. Looks nice.
2. Keeps the support hand from sliding forward off the stock with heavy recoiling and yet lightweight, rifles.
3. Acts as a position marker while resting stock on a tree stump, backpack, fallen log, saddle and so on. Thus not allowing you to pull backwards enough that the barrel touches the supporting object and destroys the accuracy.
4. The Schnabel fore-ends were usually used on thin light-weight stocks, thus the wood on the front of the fore-end tip would be very thin and likely to crack or be damaged in use. BUT, the extra thick beak (schnabel) area would stop that.
Some stocks, such as on short Mannlicher style full stocked carbines and rifles have a second Schnabel further back as a support hand reference.
Proper and consistent hand placement being very critical to accuracy with a lightweight rifle.
Many old rifles in German museums have very short fore-end wood compared to modern rifles. Those I have seen with these short fore-ends always seemed to have a Schnabel.
Down side:
1. Pretty much only works on thin lightweight stocks. So they are often too light up front for target shooting.
2. May hang-up in certain types of scabbards.
3. Thin wood in the fore-arm could be damaged more easily.